The active drug in Tylenol, acetaminophen, is one of the best medications we have for helping people in pain. It's also one of the most commonly overdosed substances in the world, and it puts about 60,000 Americans in the hospital every year. Several hundred people in the U.S. will die in 2013 from liver failure after acetaminophen overdose.

Tylenol isn't addictive like narcotics, and the kids don't take it to get high, which lends it an air of benignity and social acceptance not otherwise afforded to many pain medications. When people overdose on pills like Vicodin or Percocet, though, which contain acetaminophen, it's that component that often does the most damage.

Acetaminophen is also more accepted in that we don't think of Tylenol as a medication that alters a person's mental state. People can take it and still drive a car and go to work and remain fully present beings. But the more it's studied, the more it seems we may be overlooking subtle cognitive effects. In 2009, research showed that acetaminophen seemed to dull the pain of social rejection -- sort of like alcohol or Xanax. The author of that study, Nathan DeWall at the University of Kentucky, said at that time, "Social pain, such as chronic loneliness, damages health as much as smoking and obesity."

New research this week found that Tylenol altered the way subjects passed moral judgments. Psychologists used that as a proxy measure for personal distress, a relationship that has been previously demonstrated.

Daniel Randles and colleagues at the University of British Columbia write in the journal Psychological Science, "The meaning-maintenance model posits that any violation of expectations leads to an affective experience that motivates compensatory affirmation. We explore whether the neural mechanism that responds to meaning threats can be inhibited by acetaminophen." Totally.

More plainly, "Physical pain and social rejection share a neural process and subjective component that are experienced as distress." That neural process has been traced to the same part of the brain. They figure that if you blunt one, you blunt both. As they told LiveScience, "When people feel overwhelmed with uncertainty in life or distressed by a lack of purpose, what they're feeling may actually be painful distress ... We think that Tylenol is blocking existential unease in the same way it prevents pain, because a similar neurological process is responsible for both types of distress."

In this study, Randles's team gave 120 people either two extra-strength Tylenol or a placebo. They then primed them by asking half to write about what happens when we die (meant to invoke or replicate existential anxiety) and the other half to write about a control, non-existential topic (going to the dentist, meant to focus people on concrete things). The rationale was that "thinking about death is incompatible with everyday thoughts ... and that it leads to the same anxiety ... as frustrated social interactions or perceived incongruities."

Then all were asked how high they would set bond for a hypothetical person arrested for prostitution.

Randles et al, Psychological Science

Among people who took the placebo pill, those who wrote about existential anxiety set much higher bail ($450) than those who wrote about the dentist ($300). But if they took Tylenol and wrote existentially, that sense of moral judgment seemed to be blunted. They set the same bond regardless of the priming.

Then in a similar, separate experiment, they primed the subjects by having them watch video clips. They either watched The Simpsons or a film by surrealistic neonoir writer/director David Lynch, in which humans with rabbit heads wander an urban apartment muttering non sequiturs. They then passed judgment on people arrested in a hockey riot. Again, the people in the existential mindset imposed harsh sanctions, but the people who'd watched The Simpsons were lenient. If they'd taken Tylenol first, though, the David Lynch-induced anxiety was apparently blunted. They recommended the same sanctions as the Simpsons-primed group.

This all raises more questions than it answers. This study was small. The headlines are grandiose. The way people pass moral judgments is not necessarily indicative of their level of existential anxiety. But acetaminophen indeed appears to be affecting people's perspectives, which further muddies our already complex relationship to the drug.

As Randles sees the value of their findings, "For people who suffer from chronic anxiety, or are overly sensitive to uncertainty, this work may shed some light on what is happening and how their symptoms could be reduced."

Even though these changes in judgment are abstract and seemingly for the better, inclining people to benevolence and forgiveness, what other cognitive effects of acetaminophen might we yet discover? For the millions who take acetaminophen on a semiregular basis unaware that it might be confounding their value system, as well as the artists whose livelihoods are contingent on their work invoking profound existential angst, the question is not just academic.